OBJECTIVES: 1. Overall objective of this study is to document the teratogenic susceptibility of the fetal rat lung to abnormal development and the extent to which this may be related to subnormal function postnatally. 2. Teratogenesis is generally considered as a phenomenon to which only embryonic stages are susceptible. Our studies are designed to detect the extent to which developmental events of the fetal stages may be disrupted by exogenous agents. Because fetal developmental events are preparatory to function but not gross anatomical structures, the arrays are primarily of histology and associated physiology.